Another spell that works! Furthermore... this summons units in battles! It seems #effect 3 and 10003 don't work, but #effect 21 works just fine in battles (unless on of the summoned critters was a commander).
It's not perfect, but it is VERY interesting: this summon spell still has range 30+, and fires bolts of flame... the Hoburgs (as units) are summoned where the flames strike the ground.